The impact of localized fatigue on contralateral tremor and muscle activity is exacerbated by standing posture

Morrison, Shannon; Sosnoff, Jacob J.

doi:10.1016/j.jelekin.2010.07.002

Cited by 16 publications

(19 citation statements)

References 46 publications

(63 reference statements)

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“…white noise) (Pincus 1991). Cross-approximate entropy (Cross-ApEn) was then employed to assess the degree of synchrony between the two limbs, where a lower Cross-ApEn value would reflect greater regularity between the two signals, indicating greater synchrony between limbs (Morrison and Sosnoff 2010).…”

Section: Discussionmentioning

confidence: 99%

“…Although Cross-ApEn has been useful for assessing between-limb coupling as it examines pattern synchrony between two oscillating signals (Morrison and Sosnoff 2010;Kavanagh et al 2013), the individual frequency components of FDI EMG provided greater insight to the neural effect of removing visual feedback for a single limb. In contrast to index finger abduction force tremor, betweenlimb differences in FDI EMG emerged when visual targets were presented for both limbs.…”

Section: Figmentioning

confidence: 99%

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Removing visual feedback for a single limb alters between-limb force tremor relationships during isometric bilateral contractions

2014

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This study examined how force tremor and muscle activity are altered between limbs when a visual target is removed for one limb during bilateral index finger abduction. Isometric index finger abduction force was examined in healthy adults (23 ± 4 years) when both index fingers abducted simultaneously. Abduction forces ranged from 5 to 20% maximum voluntary contraction, and these target forces were displayed on a PC monitor in front of the subject. Force tremor and first dorsal interosseous (FDI) activity were first collected while subjects viewed visual targets for both index fingers and then when the visual target was removed for the non-dominant index finger. Subjects successfully matched the force amplitudes generated for both limbs regardless of visual condition. When the visual target was removed for one limb, force tremor increased in this limb (p < 0.01). Different power spectral profiles were evident for each FDI EMG when targets were available for both limbs (p < 0.05); however, when one target was removed, the pattern of FDI EMG for the limb without a visual target closely reflected FDI EMG for the limb which had the visual target. The CNS actively modulates muscle activity in each limb to perform visually guided isometric contractions. Given that the goal was to match force output with both limbs, the requirements of the task must be established from the limb that had a visual target, and a copy of those motor commands appears to have been sent to the FDI of the limb without a visual target.

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Section: Discussionmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

Removing visual feedback for a single limb alters between-limb force tremor relationships during isometric bilateral contractions

2014

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“…For a posturalsuprapostural task, reported an enhanced tremor coupling of adjacent segments in the upper limb during quiet stance combined with an aiming posture, as a signature of reduction in effective degrees of freedom in joint space. Localized fatigue of a single arm intensified hand-finger tremor coupling of the unexercised limb (Morrison and Sosnoff, 2010) and bilateral tremor amplitude in 8-12 Hz (Chen et al, 2011). The cross modulation in tremor dynamics was posture-dependent and more pronounced in standing than sitting (Morrison and Sosnoff, 2010).…”

Section: Introductionmentioning

confidence: 94%

Organization of physiological tremors and coordination solutions to postural pointing on an uneven stance surface

Guo

Yang

Huang

et al. 2012

Journal of Electromyography and Kinesiology

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“…Repetitive contractions of a single finger could enhance inter-digit tremor coupling at 8-12 Hz (Hwang et al 2009b). Despite that fact, however, between-limb tremor coherence is not present in the fatigue and non-fatigue states (Morrison et al 2005;Morrison and Sosnoff 2010), in support of independent tremor oscillators for bilateral limbs.…”

Section: Introductionmentioning

confidence: 97%

Global effect on multi-segment physiological tremors due to localized fatiguing contraction

2011

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Physiological tremors within a limb are coupled, whereas between-limb tremors are thought to oscillate independently for a healthy subject. This study was undertaken to reinvestigate bilateral tremor relations and intra-limb tremor dynamics for a two-limb task after exhausting a single joint. Fifteen volunteers conducted prolonged tracking with the left (target) shoulder. Neuromuscular functions were monitored before and after the exercise-fatiguing intervention, including tracking displacement, muscle activity of the deltoid, and physiological tremors in the bilateral upper limbs. Localized fatiguing contraction degraded tracking accuracy and movement smoothness, accompanied by an increase in deltoid activation. Segment tremors in the bilateral limbs and inter-limb tremor coherences in 8-12 Hz increased, though coherence peaks in 5-8 Hz waned with fatigue response. Intra-limb tremor relations in the target and non-target limbs were also reorganized with unilateral fatiguing contraction. Tremor coupling in the arm-C7 complexes was enhanced, associated with tremor uncoupling in the forearm-arm and hand-forearm complexes. Tracking error in the pre- fatigue and post-fatigue conditions was predicted by different principal components that had high communalities with tremors of distal and proximal segments of the target limb, respectively. The adaptive changes in tremor dynamics were attributable to fatigue-induced enhancement of common central drive and decline in neural inputs of long-looped reflexes that diverge to contralateral segments.

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The impact of localized fatigue on contralateral tremor and muscle activity is exacerbated by standing posture

Cited by 16 publications

References 46 publications

Removing visual feedback for a single limb alters between-limb force tremor relationships during isometric bilateral contractions

Removing visual feedback for a single limb alters between-limb force tremor relationships during isometric bilateral contractions

Organization of physiological tremors and coordination solutions to postural pointing on an uneven stance surface

Global effect on multi-segment physiological tremors due to localized fatiguing contraction

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